As one of methods to enhance a sound insulating property of a automobile interior of an automobile, there has been conventionally adopted a method of providing a sound insulating structure along a beltline of the automobile. As such a sound insulating structure, for example, Reference 1 (JP-A 2001-219738) discloses a sound insulating structure in which, at a door glass closed time, sound insulators are provided in ones of lower end portions of an outer seal portion and an inner seal portion which are mounted on a door panel, and portions corresponding to the lower end portions of the door glass, and projections elastically contacting the sound insulators are provided in the other of the above.
The sound insulating structure described in Reference 1 intends to prevent intrusion of sound from a automobile exterior by closing a gap in the door panel, concretely, between the seal portion provided in the door panel and the door glass, at the door glass closed time, and a reasonable sound insulating effect can be obtained. However, noise of a automobile interior of an automobile includes, in addition to sound intruding by air propagation from the automobile exterior, sound generated as a result that various members including a door glass vibrate. A sound insulating property of the automobile interior is expected to be improved by suppressing vibration of the door glass in particular, but in the sound insulating structure of Reference 1, a countermeasure against vibration of the door glass is not considered and a high-level sound insulating performance cannot be obtained.